1. Field of the Invention
The present invention relates to a method of manufacturing a semiconductor device, and more particularly to a method of manufacturing a semiconductor device in which a barrier insulating film for covering copper wiring is formed by use of a plasma enhanced CVD method.
2. Description of the Prior Art
In recent years, high speed in data transfer speed has been sought along with a high degree of integration and high density for semiconductor integrated circuits. Therefore, an insulating film having a low dielectric constant with a low RC delay (hereinafter referred to as a low dielectric constant insulating film) has been used.
On the other hand, with respect to a wiring material, copper (Cu) wiring having low electric resistance has come to be used instead of the conventional aluminum (Al) wiring.
Therefore, as an interlayer insulating film, a low dielectric constant insulating film is formed on copper wiring. When the low dielectric constant insulating film is formed after the formation of the copper wiring, or alternatively in steps after the formation of the copper wiring, annealing is performed at about 400 to about 450xc2x0 C. Moreover, because a high field is applied to the interlayer insulating film during the operation of the semiconductor device, to prevent diffusion of copper into the low dielectric insulating film owing to heat and electric field, a barrier insulating film is sandwiched between the low dielectric constant insulating film and the copper wiring.
However, while a barrier insulating film is dense, it has a high relative dielectric constant. Among the various barrier insulating films, a SiC-based barrier insulating film shows a relatively low relative dielectric constant of about 5. However, when a barrier insulating film having a relative dielectric constant of 5 and a thickness of 100 nm is combined with a low dielectric constant insulating film having a thickness of 500 nm and a relative dielectric constant of 2.8, the relative dielectric constant of the interlayer insulating film as a whole becomes as high as 3.02.
Therefore, while an effort has been made to make the thickness of the barrier insulating film as thin as about 50 nm, the capability to prevent copper diffusion is thereby reduced.
The present invention relates to a semiconductor device having a barrier insulating film with a low relative dielectric constant, which covers wiring formed of a copper film or mainly formed of a copper film, and relates to a method of manufacturing the same. An object of the present invention is to provide a semiconductor device having a barrier insulating film with a low relative dielectric constant, which shows a small leak current and high capability to prevent copper diffusion, and to provide a method of manufacturing the same.
In the present invention, a film forming gas containing an alkyl compound and an oxygen-containing gas is supplied between first and second electrodes, and gas pressure is regulated to 1 Torr or less. Thereafter, high frequency power of a frequency of 1 MHz or more is applied to any one of the first and second electrodes, and the film forming gas is converted into a plasma. The plasmanized film-forming gases react with each other to form a barrier insulating film covering the copper wiring.
The use of the film forming gas converted into a plasma state by only high frequency power makes it possible to produce a low relative dielectric constant film. Moreover, it is possible to maintain sufficient denseness of the insulating film to prevent copper diffusion by controlling the pressure of the film forming gas to 1 Torr or less, at least at an early stage of the film formation.
To increase the denseness of the insulating film while maintaining a low relative dielectric constant, the film formation is carried out under a pressure for the film forming gas which is gradually elevated from low pressure to 1 Torr. Alternatively, ammonia (NH3) and nitrogen (N2) are added to the film forming gas, at least at the early stage of the film formation. Alternatively, the film forming gas may contain at least one of He and Ar as a dilution gas. The flow rate of the dilution gas may be increased at least in the early stage of the film formation. Alternatively, bias power of a low frequency is applied at the early stage of the film formation.
Moreover, hydrocarbon is added to the film forming gas to enhance etching selectivity for the etchant of the insulating film with the low relative dielectric constant, which is formed on the barrier insulating film.
As described above, according to the present invention, a barrier insulating film having a low relative dielectric constant can be formed while maintaining sufficient denseness to prevent copper diffusion.